Projection system



oct. 1, '1935. H C, CONRD 2,015,034-

PROJECTION SYSTEM Filed oct'. 14, l1951 '5 sheets-sheet 1 ATTORNEYS Oct. 1, 1935.

H. c. coNoRD v 2,016,034

PROJECTION SYSTEM Filed Oct. 14, 1931 3 Sheets-Sheetl 2 Oct. 1, 1935. H. c. coNoRD 7 2,015,034

- PROJECTION SYSTEM V Filed oct. 14, 1931 3 Sheets-sheet '3 INVENTOR Patented Oct. 1', 1935 UNI-Teb STATES 'PATENT oFFiciE 2,016,634 y PROJECTION sYs'rE'M ,Herben c.- conord, Bookiyn, N. Y., signor to Trans-Lux Daylight Picture Screen Corporation, New. York, N. Y., a corporation, of Delaware Application october-14,1931, smal No. 568,665

' 4 claims. (ci. iis- 24) or equivalent.

My invention, in a prominent phase thereof,

l relates to adjusting mechanism for the projection. lens of a projector mechanism and, more particularly, my invention involves an arrangement for angularly relating the axis of a projection lens to a line extending perpendicularly with respect to the center of any given iilm section while the latter is in the projection field of said projector mechanism.`

Further objects, advantages andcliaracteristics of my invention will become apparent fromthe following detailed description taken in connection with the accompanying drawings.

My invention resides in the projector mechanism, adjustable projection lens support or mount,

and other features of the character hereinafter ,Y

' member 2 being horizontally slidable with respect described and claimed, -For an understanding of my invention and for an illustration of some of the many forms thereof, reference is to be had to the accompanying drawings, in which: l Y

Figure 1 is a plan view, partly in section and partly broken away, showing a projection lens positioned in accordance with my invention;V

Fig. 2 isA a side elevational view of a support for a projection lens;

Fig. 3 is an end elevational view, partly in section, of the support' shown in Fig. 2;

Fig. 4 is a bottom view of the support shown in Fig. 2;

Fig. 5 is a diagrammatic arrangement;

Fig. 5a is an elevational view showing .the end of a projection lens;

Fig. 5b is a diagrammatic view illustrating keystone distortion on a screen;

Fig. 6 is a diagrammatic view of a projection arrangement in accordance with my invention;

Fig. 6a is an elevational view showing the end of a projection lens; y

Fig.'6b is a diagrammatic view illustrating a screen image area after removal of screen distortion;

Fig. 7 is a plan view, partly insection, of

manner so that the axis of said projection lens view of a projection in plan and is taken o n the line Ill- I0 o1' Fig. 9 looking in the directionof the arrows;

Fig. 11 is a view in plan of a part of Figs. '7, 8, and 9 looking upwardly. l

. In general, my invention relates to an arrange- 5 ment for substantially or largely eliminating keystone distortion on a motion picture screen. To this end, I mount the projection lens of a suitable projector mechanism in an adjustable or pivotal l0 may be angularly related to a line extending perpendicularly with respect to the center of fany given lm section while the latter is in the pro'- jection field of the projector mechanism.

For one form of mechanism which has proved satisfactory in operation for the purpose stated, reference is to be had to Figs. 1, 2, 3, and 4 wherein C illustrates the center frame of any suitable projector such, for example, as is known in the v art as a Simplex projector. Carried by the frame 20 C in dove-tail relation are members I and 2, the

In accordance with my invention, abracket 3 25 A is suitably secured to the member 2. As shown in Figs. 2, 3, and 4, thefbracket 3 comprises vertical and horizontal sections 3a and 3b, the vertical section 3a, preferably, comprising a plurality of elongated slots 3c through each of which extends 30 a clampingscrew 4, the screws 4 being threaded into the member 2, and the heads of said screws 4 coacting with the walls of the respective slots 3c. By virtue of this arrangement the bracket 3 may be vertically adjusted as desired and thereafter 35 positively held in a desired position under the iniluence of said screws 4.

. bracket 3 is the holder 5 which receives the barrel B of any suitable projection lens. As illustrated, 40 the holder 5 comprises a at surface 5a which rests uponthe upper ilat surface of the aforesaid horizontal bracket section 3b.

In accordance with one form of my invention, said horizontal bracket section 3b comprises a 45 pair of spaced parallel slots 3d, 3d, Fig. 4, eachslot slidably receiving a block 6. Swivelled to each block 6 is a screw 1, each screw 'I extending through a passage in the outer part of the horizontal Abracket section 3b and being threaded 50 thereto. Threaded through each block 6 is a screw 8 which, at its end, is threaded into the aforesaid ilat surface 5a of the holder 5. The screws 8 are adapted to exercise a clampingef- Vfect upon the lowersurface of the horizontal bracket section 3b and, therefore, each of said screws 8 comprises a clamping section 8a beyond which extends the portion of the screw adapted for manual manipulation.

As is usual, the holder 5 may be a split ring, opposite sections of which are flanged for the reception of a clamping screw 9. Furthermore, the holder 5 may have a light-opaque cylinder I0 associated therewith, said cylinder I0 being telescopically related to the holder 5 in freely slidable relation. Inaccordance with usual practice, the outer end of the cylinder I0 may comprise a laterally extending anged section Illa to which, at approximately diametrically opposite sides thereof, ends of the respective rods II are xedly secured, each rod II being disposed outwardly of the cylinder I0. As clearly appears in Fig. 3, the holder 5 comprises lugs 5b, 5b disposed at approximately diametrically opposite sides thereof,

these lugs being provided with passages for the,

free slidable reception of the respective rods II. Disposed about each rod I I is a helical spring I2,

one end of each ofy `which engages the flangedsection Illa of the cylinder I0 and the other ends of which engage the respective lugs 5b. Accordingly,- it results that the cylinder I0 is biased from sembly, the lm driving mechanism, and other mechanical details of such projectors are well understood by those skilled in the art and, therefore, a detailed description of such characteristics of these prior art projectors need not be i'ncluded in this specification.

Accordingly, in Fig. 1, I have merely shown the projector arrangement in a general manner as comprising the film trap assembly I3 which is detachably secured to 'the projector center frame C. This lm trap assembly comprises the usual lm guiding wheels I4 and I4a, and the movable gate I5. The lm F, which preferably is ordinary motion `picture film, is shown in the film trap assembly between the members I3 and I5 and, in the relation shown in Fig. 1, said film F travels in a direction approximately at right angles to the plane of the sheet of drawing paper.

As is well understood, the lm trap assembly comprises a transverse passage, namely, the projection eld or picture aperture through which .the projection light beam passes from left toA right, Fig. l, sections of said lm F passing successively through the aforesaid projection eld.

- Beyond the film trap assembly, the projecting screen, the projecting light beam being reflected Ato the audience byrsaid screen. Rear projection,h

with its attendant advantages, is also well understood. In rear projection, the audience area and the projecting'light beam passing `through the screen in order to reach the audience.

In front projection, due to the size of the auditorium area,-the projector may be disposed a relatively great distance from the screen and, therefore, a projection lens of relatively long focus may be utilized. Since the space behind the screen is relatively small, the projector, for rear projec- V tion, is positioned relatively close to the screen,

this necessitating the use of a suitable short focus projection lens such, for example, as the positivenegative lens combination described in U. S. Letters Patent No. 1,863,099, the barrel B being herein shown as having such a positive-negative lens combination disposed therein.

For front projection, therefore, the throw" between projector and screen is relatively long while, for rear projection, the throw is relatively f short. As is well understood, for the presentation of multi-reel motion pictures, it is common practice to utilize at least a pair of projectors disposed, respectively, at opposite sides'of the screen center line. Due to the long throw existing in ordinary. front projection, the disposition of the projectors on the respective opposite sides of the 2 screen center line introduces no serious operating difficulties as regards the obtaining of screen images having proper definition. However, the disposition of the projectors at the respective opposite sides of the screen center line and the positioning of said projectors Arelatively close to the screen as practicedin rear projection introduces serious difficulties as regards imagereproduction.

To overcome such defects, it is'necessary vthat cer- I tain-'corrective measures be taken and, itis forthis purpose, that the hereinbefore described mechanism is utilized.

In Fig. 5, I have illustrated the projector P as disposed to one side of the screen center line L and preferably at about the same Ahorizontal level, .t

the projector being approximately the distance from said center line L which is necessary-if there is to be suicient space between the pair of projectors for the operators thereof to properly attend to'their duties. The axis LI of the projecting light beam from the light source and the axis through the projection. lens or the barrel B thereof substantially coincide, the line LI intersectf ing the screen S substantially at the center thereof. Under such circumstances, where the projector P is laterally spaced from the screen center line as above stated, it results that the screen images andthe peripheral boundary of the screen image area are distorted and of keystoneconfiguration somewhat Aasrillustrated to an exag- 5 gerated degreein Fig. 5b. j j,

I have discovered that this keystone effect may be substantially overcome by first bodily shifting the projector and the projection lens asa; unit,

lens with respect tothe projector so that vthe axis thereof is angularly related with respectv to a line 'extending perpendicularly fromthe' center of any given lm section while the latter is in Cil Y a'nd by thereafter bodily shifting theprojection 60 the projection field of said projector 65 Thus, the projector P is shown in Fig. -6 after it has been moved in a counterclockwise direction from the position thereof indicated in Fig. 5. I

` have found in practice thatthe new .position to 'which the projector is thus moved is preferably 70 is shifted from the screen center andthe image 75 f the projection field of the projector mechanism.

Usually, several adjustments are required of the projector as a Aunit and the projection lens independently of the projector in order to obtain the desired optical eiect, i. e., the proper disposition of the image area on the screen substantially free from keystone distortion. It is for the purpose of vsecuring the 4above describedadjustment of the projection lens independently of the other projector parts that`I,

utilize the mechanism hereinbefore-described. As

stated, the projection lens barrel B is carried by image area off the screen as hereinbeiore4 dekscribed, it results that the projection lens moves therewith.'

In order to secure adjustment of the projection lens with respect toI the projector, the clamping screws 8 may be slightly retracted while still leaving them in engagement with the flange 5a of the holder 5. Then, with the clamping screw 8 to the right, Fig. 4, held stationary, the screw 1 to the left, Fig. 4, maybe vadvanced or retracted Yto swing the holder 5 in one direction or the other as may `be required. As stated, the holder 5 carries the barreLB of the projection lens and, therefore, the projection lens partakes of the movement impartedto said holder 5. l

Alternatively, the Aclamping screw 5 to the left,

Fig. 4, may be held stationary, the screw 'I to the' right, Figfi, being eitheradvanced or retracted to swing'the holder 5 in one-direction or the other' as may be desired.

In the manner described above, the projection lens may' be shifted in the desired manner. In' the example shown, it is important to note that the two screws 1 may be slmultaneouslyadjusted to impart lateral movement only to the holder 5 and likewise to the projection lens carried thereby.` Therefore, with the forni` of -niy invention show n in Figs. 1-4 inclusive,the mechanism comprising the screws 1 and 8 may beused forad-v justing the barrel 5 'angularlyz in the manner stated arid also laterally. This isadvantageous but my invention is not t'o be limited in this respect. Y

As stated, the cylinder l is carried by. the barrel and, therefore, these two members Amove together during angular 6r lateral adjustment of said barrel 5. In operation, thecylinder IIL rests against the gate I5 of the lm trap assembly as' clearly appears from Fig-1. In Fig.-5b, I 4have illustrated the keystonefe'ect which, in accordance with my invention, is

f substantially'overcome as clearly appears from a. considerationV of Fig. 6b.

InFigs. 5a and 6d, I have illustrated the end of ligh'tbeam which occurs due to thehereinbefore 5- describedi angular adjustment of vthe projection lens.

For a modifledform of my invention, reference is to be had to' Figs. 7, 8, 9, and lo'wherein a bracket is shown as comprising a vertical sec- 1o tion 20a and a horizontal section 20h, the vertical section 20a preferably comprising an elongated 'slot 20c, Fig. 8, through which extends a screw 2 I threaded into thehereinbefore described member 2, the head of said screw coacting with the l5 exterior surface ofthe aforesaidvertical section adjacent the slot 20c.

Carried by the horizontal section 20h of the bracket 20 is a U-shaped bracket 22 having upwardly extending arms-to which the herein- 20 before described holder 5 is suitably secured. Preferably but not necessarily, the holder 5 is secured to the bracket 22 by screws 23, 23 which extend'loosely through the respective opposite arms of the bracket22and arev threaded into 25 the barrel 5 at diametrically opposite sides thereof. By virtue of this arrangement, the holder 5 is swivelled for pivotal movement in a vertical direction, Fig. 9, with respect to the bracket v22.

The holder 5 and bracket 22 are adapted for 30 pivotal horizontal movement together on the horizontal arm 20h of the 'bracket 20 andsaid holder 5 and bracket 22 are also adapted for horizontal movement together from left to right v or'vice versa, Eig. A9. For this purpose. an arrangement of anysuitable character may be utilized. As shown, the horizontal bracket arm 2Gb is provided with an elongated slot 20d slid- Y ably receiving a block 24 through .which extends the shank of a screw 25 threaded into 'the horizontal section of the bracket 22, the screw 25 havingV an operatinghead 25a. As illustrated, the block 24 may be biased from right to left, Fig. 9, by a helical spring 26 whereby said block .24 isheld in engagement with an adjusting screw 2l threaded through lthe en d of the bracket arm 20v. As will be hereinafter pointed out, the mechanism just described is utilizable for so adjusting the holder 5 and the thereby-carried projection lens that the axis thereof is angularly 50 relatedv in suitable manner to a line extending prpendicularly with respect to the center of any given lm" section while the latter is in the pro- I-jection eld'of the projection mechanism.

Depending' from the holder 5 area pair of 55 spaced ears 28,(@28a through which extends a member 29 upon-'which a depending threaded shank 30 is pivoted. Depending from the bracket l23 'and' suitably secured thereto is a bracket arm'3l carrying. a clevis-like member w -32 soperforated that the shank 30 extends freely therethrough. Disposed betweenfthe arms of the 1 member 32 is a'. thumb nut 33 through which .said .shank 30 extends in threaded relation, Furthermore, the shank also preferably carries a pair 65 of lock nuts` 34, 34a coactable with the respective arms of the member 32; u I

If desired,the extreme end of the horizontal bracket section Zlibl may be 'widened and serrated or notched as indicated in Fig. Al0. Coactable In operation, the holder s 0i may, a, and 9, u

carries a projection lens and barrel the .same

as the corresponding parts of Figs. 1, 2, 3, and 4.

y When the axisl through this projection lens is to be-shited, the screw 25 is slightly retracted whereby the barre1-5 and the bracket 22 may be manually swung to a desired extent in either a clockwise or counter-clockwise direction, Fig.`

7. Thereupon, the screw 25 may be tightened to positively retain the barrel and bracket 22 in the position to which adjusted. By virtue of this adjustmenttogether with the bodily adjustment of the projector 'as hereinbefore described, the image area may be properly centered on the screen while at the same time substantially or largely eliminating keystone distortion therefrom.

The adjusting mechanism described above is utilized when-the projector is disposed approximately at the same horizontal level as the screen center' line. In case the projector is disposed a substantial distance either above or below said screen centerline, it may be desirable to correct ing mechanisms are provided as shown in. Figs.

'7, B, 9, andl 10, the keystone distortion may be eliminated no matter whether the projector isA approximately horizontally to one side` of or vertically above or below the screen center line.

j In addition to the foregoing and after slight retraction ofthe screw 25, the screw 2T may be operatedto shift the block 24 either to the right or the left, .-Fig. 9, whereby the holder 5 and the thereby-carried projection lens may be shifted laterally in a horizontal direction.

The last descr-ibedmovement of the projection lens-together with that lateral lens movement described in connection with the simultaneous adjustment of the screws 11 of Figs. 1-4 is utilizable in connection with the two kinds of motion picture film now in commercial use, i. e.,

'the type having a soundtrack at one side of' thepicture frames and the type omitting said sound track. As well understood in the art, it

is necessary to provide for such lateral adjustment of the projection lens so that the projector may use either of the two types of lm above noted.

The hereinbefore described pointer 35 partakes of such pivotal adjustmenty as is impartedto the holder 5.l Accordingly, on the bracket section 20h, there is obtained an indication concerning the degree of pivotal adjustment of the holder 5 and the thereby-carried projection lens. It shall be understood that the indicating mechanism just described may'v be omitted if desired When the two adjustl since my invention is not to be limited thereto.

It will be understood that various mechanical changes may be made without departing from the spirit of my invention. Thus, one of the screws 1 together with the block 6 associated 5 therewith as shown in Figs.. 1-4 may b e omitted, a single screw 1 andv block 6 being suiicient to obtain the desired adjustments. In the arrangement of Figs. 7-9 inclusive, the screw 21 may be swivelled to the block 24, in which case the spring 10 26 may be omitted. Similarly, other mechanical changes may be made as desired.

While the inventionr has been ydescribed with respect to certain particular preferred examples which give satisfactory results. it will be under.- stood by those skilled in the art after understanding the invention, that various changes and modications may be made without departing from the spirit and scope of the invention and it is intended therefore in the appended claims to cover all such changes and modications.

What is claimed as new and desired to be secured by Letters Patent is:

l. In a projector having a center frame, a 25 bracket carried' thereby and having a horizontal arm, a projection lens holder slidable on said bracket arm toward and from said center frame, and means for pivotally supporting said holder on said bracket arm for movement substantially in a horizontal plane whereby the projection lens axis may be angularly related to a line extending perpendicularly withrespect to-the center of any given lm section while the latter is in the projection field of said projector.

2. In a projector having a' center frame, a a bracket carried thereby andI having a horizontal arm with a slot, a block movable in said slot, and a projection lens barrel pivotally mounted on said block.

3. In a projector having a center frame, a bracket carried therebyand having a horizontalarm with a slot, a block movable in said slot, means for adjusting said block toward the respective opposite ends of said slot, a projection lens barrel pivotally mounted on said block,

and means `ior positively retaining said barrel in a pivotally adjusted position.

4. In a projector having a center frame, a bracket carried thereby and having a horizontal arm, a projectiony lens holder slidable on'said bracket arm, means for moving said projection lens holder toward and from said center frame while maintaining the axis thereof in a horizontal plane, and means for pivotally supporting said projection lens holder on said bracket arm for movement substantially in a horizontal plane whereby the projection lens axis may be 'angularly related to aline extending perpendicularlywith respect to the center of any given iilm sectionwhile the latter is in the projection field of said projector.

HERBERT C. CONORD. 

